Semiconductor fabrication facilities normally include several fabrication tools located in a clean room. The fabrication tools robotically implement the sophisticated photolithographic process which involves dipping semiconductor silicone substrates in chemical baths. High efficiency air filtration systems are used to reduce particulates in the clean room that may contaminate the processes. In addition, some of the fabrication tools are provided with ultra high efficiency filtration units positioned over critical process areas to further reduce the potential of contamination. The chemical vapors can be extremely corrosive. Most if not all of the tools are equipped with fume exhaust systems which exhaust the chemical vapors from the tool to fume conditioning equipment for the facility.
The potential for fire exists in semiconductor fabrication tools not only due to the combustible nature of semiconductor materials, but also because of the materials and design of the fabrication tools. For example, most semiconductor fabrication tools include electrical heating elements or other heat producing equipment that is located in close proximity to plastic composite materials. Therefore, upon failure of a heating element or some other type of failure, the plastic composite materials of the tool structure may melt, thus generating combustible vapors that support propagation of fire to adjacent materials. This type of burning of plastic composite materials generally produces large particulate smoke which is harmful to the affected tool and also to adjacent processes in the clean room fabrication facility.
While clean room semiconductor fabrication facilities are normally equipped with conventional fire suppression systems such as sprinklers, it is normally desirable to equip the individual tools with dedicated fire detection and suppression equipment. Individual fire detection and suppression systems are used because it is desirable to avoid the initiation of sprinkler discharge from the facility fire suppression system into the clean room which is likely to damage or at least contaminate several if not all of the individual tools. One type of fire detection and suppression system used on individual semiconductor fabrication tools uses high pressure carbon dioxide as a fire suppression agent. When a fire is detected in or near the tool, these systems release carbon dioxide into the individual tool from high pressure carbon dioxide canisters. Once the discharge cycle is initiated, the system must discharge completely due to the nature of high pressure carbon dioxide discharge systems.
Obviously, it is important that the fire protection system for the clean room and for the individual fabrication tools reliably detect fires, and suppress detected fires efficiently in order to reduce the likelihood of damage to the surrounding area including inter-exposed semiconductor fabrication tools. On the other hand, the discharge of fire suppression agent in response to a false alarm can be extremely costly for the facility. The discharge of suppression agent can cause substantial harm and contamination to the individual fabrication tools, as well as lead to significant downtime for clean-up. In many cases, the cost of downtime associated with the clean up after a false alarm is substantially greater than the actual cost of clean-up and repairs.
One of the main drawbacks of using high pressure carbon dioxide fire suppression systems on individual tools is that the discharge of suppression agent cannot be terminated once the discharge cycle begins. Thus, even in a false alarm situation, high pressure carbon dioxide fire suppression systems discharge normally creates significant harm and contamination to the tool and also leads to significant downtime for the tool and/or facility.